Academic literature on the topic 'Screw channel surface'
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Journal articles on the topic "Screw channel surface"
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Chayka, Yevgeniy, Viktor Zhurba, Natalia Krivtsova, Anna Khadzhidi, Pavel Voshchevoz, and Natia Ugrekhelidze. "Experimental study on vegetation removing from irrigation channels." E3S Web of Conferences 175 (2020): 09007. http://dx.doi.org/10.1051/e3sconf/202017509007.
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The parameters of the process of vegetation removing from the water surface have been justified. An experiment was conducted to determine the strength of the screw-type tool and matching the most appropriate parameters. It was established that the channel clean-up quality depends on the screw diameter. It was also investigated the influence of the screw rotation speed on the channel clean-up quality. The dependence of the cleanup quality on the flight screw pitch has been determined.
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Kimura, Koichi, Yusuke Itamochi, and Hideki Tomiyama. "The Evaluation of Mixing Characteristics of Dulmage Screw." Advanced Materials Research 747 (August 2013): 769–72. http://dx.doi.org/10.4028/www.scientific.net/amr.747.769.
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The mixing performance of Dulmage screw was studied experimentally and numerically. In the experiment, Low density polyethylene and red colored mastebatch were mixed and extruded by using Dulmage screw or Full Flight screw. And then, the degree of color uniformity was measured on the cross-section of the extrudate. The masterbatch was distributed more uniformly on the cross-section of Dulmage screw than that of Full Flight screw. The degree of color uniformity for Dulmage screw was about two times higher than that for Full Flight screw. In the numerical analysis, the flow pattern of the masterbatch in the screw channel of Dulmage screw was visualized by means of particle tracking technique. The degree of the distribution of the masterbatch was quantified as the information entropy. The information entropy at the outlet of the screw changed periodically with the screw rotation speed. Furthermore, the masterbatch circulated between the screw surface and the barrel surface in the fin section, consequently the degree of the distribution of the masterbatch changed periodically. In case the masterbatch was distributed uniformly along the channel depth at the outlet of the fin section, the information entropy at the outlet of the screw became high. The result shows the mixing performance of Dulmage screw strongly related to the degree of the distribution of the masterbatch at the outlet of the fin section.
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Xie, Peng Cheng, Gang Gou, Zhen Xing Wen, Yu Mei Ding, and Wei Min Yang. "Research on the Key Technology of Precision Injection Molding Equipment for Light Guide Plate." Advanced Materials Research 87-88 (December 2009): 306–10. http://dx.doi.org/10.4028/www.scientific.net/amr.87-88.306.
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The light guide plate is an important element of the LCD backlight module which demands a certain degree of transparency and uniformity of gray. The defects such as black spots and yellow surface appeared when the light guide plate was processed by domestic equipments. The main problem was caused by the plasticization unit. The Influencing factors of performance for polycarbonate (PC) special screw were discussed in this paper. The conveyance capacity of melt in the metering zone of injection screws with different flight width and channel depth was analyzed by POLYFLOW software. In order to obtain high surface hardness, corrosion resistance and smoothness of PC special screw, surface coating processing was the key point for injection molding light guide plate. Moreover, the peel strength of PC with different coating processing metallic block was tested and measured. he experimental results of the analysis showed that the nickel-tungsten alloy plating and physical vapor deposition can significantly improve stripping properties, corrosion resistance and smoothness. The influencing factors of coating and PC materials’ stripping were analyzed. Through industrial testing, the defective rate of light guide plate had been greatly reduced with physical vapor deposition compared to the screw with hard chromium plating.
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Popa, Camelia Lacramioara, and Viorel Popa. "Graphic Method Profiling of the End Mill Cutter Generating the Screw Compressor Rotor." Applied Mechanics and Materials 658 (October 2014): 123–28. http://dx.doi.org/10.4028/www.scientific.net/amm.658.123.
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Helical rotors, components of screw compressors have different structural shapes: rotors circular front section, rotors elliptic front section or asymmetric rotors. Manufacturing rotors involves profiling a tool bordered by a revolution surface, enveloping of each helical channel. This paper proposes a method developed in AutoCAD, in order to determine the profile of end mill cutter which generates the helical channel. Graphic method is based on the principle of complementary theorems' "Substitute Circles Family Method" component of envelope surfaces theory.
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Biyani, Rashmi, Mohsin Ali, Donald Belles, and John M. Powers. "Effect of Metal Extension of Crown in the Screw Access Channel of a Posterior Implant Abutment on the Retention of Cement Retained Prosthesis." Journal of Oral Implantology 41, no. 5 (October 1, 2015): 537–41. http://dx.doi.org/10.1563/aaid-joi-d-13-00072.
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Purpose: Reducing the height of the implant abutment due to limited interarch space decreases the surface area for retention of cemented restorations. The purpose of this in vitro study was to see whether engaging the screw access channel with metal extension compensates for the loss of retention of posterior crowns cemented on shorter abutments. Material and Methods: Four identical prefabricated abutments were mounted on implant replicas embedded in acrylic resin blocks. Three of these abutments were reduced in height by 1 mm, 2 mm, and 3 mm respectively and one was left unmodified. Two sets of base metal crowns were fabricated for each abutment, one without and one with the metal extension inside the screw access channel. The crowns were cemented using Tempbond NE. The tensile forces required to separate the cemented crowns from abutments were measured using an Instron testing machine. Statistical analysis of the data was performed using a 2-way analysis of variance and Fisher's protected least significant difference at 0.05 level of significance. Results: An increase of 24% to 261% in retentive forces was observed for the group having metal extension in the screw access channel. Statistically significant differences (P < .001) were found among 2 types of crowns and four heights of abutments. Generally, the retentive forces were reduced in magnitude as the abutment height was reduced. Conclusion: The retention of a casting cemented to posterior implant abutments is influenced by the height of the abutment and the metal extension engaging the screw access channel. The crowns made with a metal extension showed superior retention values.
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Schoenbaum, Todd R., Yi-Yuan Chang, and Richard G. Stevenson. "Screw Access Mark for Cemented Implant Crowns: A Universal Technique to Simplify Retrievability." Journal of Oral Implantology 44, no. 1 (February 1, 2018): 71–73. http://dx.doi.org/10.1563/aaid-joi-d-17-00147.
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The use of cemented implant prostheses for partially edentulous patients continues to increase in clinical practice. One of the primary complications of the cemented implant crown is difficulty in retrieval, should the need arise. Drilling through most prosthetic materials is of little difficulty for most clinicians, but the complication lies in determining where exactly the access hole needs to be drilled. During fabrication, the location of the screw access channel is marked with a strong contrasting color stain on the surface of the prosthesis. The technique proposed here marks the location of the screw access directly on the prosthesis, thus improving the ease and predictability of future retrieval.
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Saninsky, V. A., E. A. Fedyanov, and E. N. Nesterenko. "CALCULATION OF PARAMETERS OF CHANNEL THROTTLING OF EXPENSIVE ELEMENTS OF FIRMWARE." IZVESTIA VOLGOGRAD STATE TECHNICAL UNIVERSITY, no. 8(243) (August 28, 2020): 50–53. http://dx.doi.org/10.35211/1990-5297-2020-8-243-50-53.
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The article considers possible options for supplying coolant to the cutting and deforming teeth of multi-pronged firmware for processing deep holes. The advantages and disadvantages of each scheme are indicated. It is noted that when the lubricant-cooling liquid (coolant) is pushed through straight or screw slotted grooves made on the outer surface of the mandrel teeth, "damping pads" are created on the surface to be processed, which improve the mandrel process and reduce wear of the stitches for processing deep holes. For each of the schemes, a method for calculating the coolant flow rate is described, depending on the parameters of the slotted grooves for the coolant flow and the pressure of its supply. The ability to calculate the consumption of coolant through the cutting and deforming teeth of multi-toothed stitches allows you to correctly assign processing modes and, thereby, increase the technical and economic efficiency of mechanical processing of long pipe blanks.
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Zitzenbacher, G., and G. R. Langecker. "A New Plasticating Model for Amorphous and Semi-crystalline Polymers in Single Screw Extruders." International Polymer Processing 20, no. 4 (August 1, 2005): 360–68. http://dx.doi.org/10.1515/ipp-2005-0064.
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Abstract Polymeric thermoplastic materials can be subdivided in amorphous and semi-crystalline ones. In contrast to semi-crystalline polymers amorphous thermoplastic materials have no defined phase transition and hence no melt enthalpy. The glass transition region describes the change of the material behaviour from the state of a rubber like to an under-cooled fluid (glassy state). Setting the melt enthalpy in the Stefan-Neumann problem zero gives no valid results for the solid bed profile. Thus this condition is unsuitable for describing the plasticating process of amorphous polymers. In this paper a new model for the plastication of amorphous and semi-crystalline polymers in single screw extruders is presented. Therefore a new calculation method for the determination of the moving velocity between the glassy solid bed and the softened film region on the barrel surface is developed. The whole enthalpy to heat up the polymer on a critical flow temperature in the screw channel is considered.
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Zhelykh, Vasyl, Malgorzata Ulewicz, Krystyna Kozak, Olena Savchenko, and Mariana Kasynets. "Analysis of the Influence of the Heat-Absorbing Surface of an Air-Cooled Solar Collector on its Thermal and Mechanical Properties." System Safety: Human - Technical Facility - Environment 1, no. 1 (March 1, 2019): 481–89. http://dx.doi.org/10.2478/czoto-2019-0062.
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AbstractThis paper presents the analysis of existing forms of heat absorbing surfaces of air solar collectors, which gained the greatest popularity in the world. The obtained data allowed to conclude that there is a need for the development of solar collectors with air as a coolant with an improved form of heat absorber, which will reduce the operational and capital costs of solar systems and allow the efficient use of such structures in a moderate climate without additional mechanisms for the transfer of coolant. The use of computer simulation helped to compare the thermal characteristics of air-borne solar collectors of a different design. The substantiation of the expediency of installing as a heat absorber of flow turbulators in the form of a screw has been fulfilled, as well as the height of the air channel of the solar collector has been determined, in which the maximum heating of the transfer medium is observed. In addition, the loss of pressure in the air channel of the solar collector with flow turbulators was determined and the comparison of the obtained data with the values of pressure losses in the air collector of the matrix type and the air collector with V-shaped ribs was made.
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Фоменко, Екатерина, Ekaterina Fomenko, Альберт Нугманов, and Albert Nugmanov. "Velocity Control of Visco-Elastic Materials Movement in the Cylindrical Channel of the Grinder Feed Screw of the Former." Food Processing: Techniques and Technology 49, no. 1 (June 26, 2019): 113–19. http://dx.doi.org/10.21603/2074-9414-2019-1-113-119.
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The present research features the problems of wheat processing. Wheat processing has its own specific features. For instance, the process of gluten extrusion forming is very complex since it is associated with the visco-elastic and adhesive properties of raw gluten. The article discusses the results of applying the numerical finite difference method to the Navier-Stokes equation in the case of the one-dimensional problem when a cooled viscoelastic material has to pass through circular nozzles. The paper also features the obtained surface model of velocity evolution and some averaged results for the possible automation of the process. The viscosity properties of raw gluten are variable and depend on temperature, chemical composition, and properties of the raw material. Modeling makes it possible to characterize the properties of the material and its behavior in various situations. Such research demands neither additional time nor significant costs. The authors identified patterns of movement for raw gluten in the extrusion molding unit and selected the most appropriate automation system to control the speed of its movement to the molding assembly in the grinder feed screw. The significance of the research is obvious for subsequent physical and mathematical modeling of heat and mass transfer processes of vacuum freezing and drying and granulating of gluten extrusions. The results of the research presented in the article are consistent with the available information on this topic. The present approach to solving the problem of choosing the best rational hydrodynamic regimes was applied due to the complexity of the experimental determination of velocity fields and the difficulty of analyzing the Navier-Stokes system of hydrodynamic differential equations with variable proportionality coefficients.
Dissertations / Theses on the topic "Screw channel surface"
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Шоман, Ольга Вікторівна. "Геометричне моделювання променевого енергообіну між аналітично заданими поверхнями." Thesis, Київський державний технічний університет будівництва i архітектури, 1998. http://repository.kpi.kharkov.ua/handle/KhPI-Press/20364.
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Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.01.01 - прикладна геометрія, інженерна графіка. - Київський державний технічний університет будівництва i архітектури, Україна, Київ, 1998. Дисертацію присвячено розробці геометричного методу обчислення кутових коефіціентів випромінювання (ККВ) щодо променевого енергообміну між аналітично заданими поверхнями. В методі здійснено побудову радіально-паралельних проекцій (RP-npoeкцій) поверхонь засобами комп'ютерної графіки. Кутові коефіціенти випромінювання отримано для випадків енергообміну між каналовими поверхнями. Алгоритми реалізовано у вигляді PASCAL-програм. В методі враховано наявність характерного для каналових поверхонь ефекту самозатінення. Розв'язано задачу самоопромінювання гвинтової каналової поверхні для витка. Результати дисертації знайшли впровадження в наукових дослідженнях оптичних систем передачі інформації, в розробках сучасних теплообмінників, у проектуванні установок полімеризації ізоляційного покриття дротів.Thesis for a candidate's degree by speciality 05.01.01 - applied geometry, engineering graphics. - Kyiv State Technical University of Building and Architecture, Ukraine, Kyiv, 1998. The dissertation is devoted to the creation of geometrical method for view factor definition during radiation energy exchange between surfaces presented by analytical form. In this method construction of radial parallel projections (RP-projections) of surfaces has been carried out by means of computer graphics. View factors have been obtained for cases of energy exchange between channel surfaces. Algorithms have been realized as PASCAL-programs. Typical channel surfaces effect of hiding parts of surface by itself has been taken into account in the method. The self-irradiation problem of screw channel surface has been solved for the whole turn. The results of the work have found an utility in the scientific investigations of optical systems of transmitting information, in elaborating modern thermal energy exchange devices, in the design of wire isolation polymerisation units.
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Qazali, Ahmad A. "Surface changes and screw loosening of the titanium abutments for one-piece implant supported fixed complete denture." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1466018689.
Full textBook chapters on the topic "Screw channel surface"
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Horng, J., XC Liu, J. Thometz, and C. Tassone. "Effect of adjunct thoracoplasty on Adolescent Idiopathic Scoliosis patients’ 3D back contour." In Studies in Health Technology and Informatics. IOS Press, 2021. http://dx.doi.org/10.3233/shti210440.
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The aims of this study were to evaluate the effect of a thoracoplasty procedure in addition to a posterior spinal fusion and instrumentation on an Adolescent Idiopathic Scoliosis (AIS) patient’s 3D back contour as measured by surface topography. We performed a retrospective review to identify patients who were treated with posterior spinal fusion with spinal instrumentation and those who were treated with an additional thoracoplasty procedure. We analyzed changes in surface topography measurements between these two groups using t-test and ANCOVA statistical analyses. Although there were no statistically significant differences in 11 of 12 variables, thoracoplasty-posterior spinal fusion (n=10) group had a mean 6.6 unit reduction in trunk asymmetry while the posterior spinal fusion group (n=26) had a mean 22.8 unit reduction in trunk asymmetry (p-value<0.05). The posterior spinal fusion group and thoracoplasty-posterior spinal fusion group were not shown to have clinically significant differences in 3D back contour correction. An additional thoracoplasty procedure does not provide better correction in the transverse plane and in fact had a smaller degree of trunk asymmetry correction. This supports the current trends of decreasing use of thoracoplasty in AIS patients to address severe rib hump deformities given concerns for decreased post-operative lung function and alternative methods of vertebral body derotation, such as thoracic pedicle screws.
Conference papers on the topic "Screw channel surface"
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Tang, Qian, Yuanxun Zhang, Linqing Pei, and Jiong Tang. "Optimal Design of Screw and Flow Field Analysis for Twin-Screw Pump." In ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/detc2011-48056.
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A new solving transcendental equation method combining graphics and analyzing approach—Matlab Anonymous Function Method (MAFM) was developed to solve the screw contact line equation. The influence of contact line on screw sealing property was revealed and the effect of involute meshing angle on the screw contact line properties of type A twin-screw pump was investigated. The tooth profiles, spiral surface equations and contact line equations of type A twin-screw pump were obtained based on the optimal involute meshing angle. The three dimensional model and flow field digital model with modified involute meshing angle for screw rotors was developed to analyze the pressure field, velocity field and other screw pump’s characteristics by applying finite volume method, and the volumetric efficiency of flow channel for twin-screw pump study has been gained. The study provides the theoretical basis for the further screw pump development and property evaluation.
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Glezer, B., H. K. Moon, J. Kerrebrock, J. Bons, and G. Guenette. "Heat Transfer in a Rotating Radial Channel With Swirling Internal Flow." In ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/98-gt-214.
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This paper presents experimental results for heat transfer in swirling internal flow, obtained in two ways. A test rig simulated a rotating blade’s leading edge internal passage with heated walls and screw-shaped cooling swirl generated by flow introduced through discrete tangential slots. Spatially resolved variations of the surface heat transfer coefficients were measured in the rotating rig using an IR radiometer. A blade tested in the actual engine environment had similar geometry of the leading edge cooling passage. The blade surface temperatures were mapped in the engine with thermal paints and compared with a traditional convective cooling configuration. The data from the rotating rig and engine measurements are also compared with non-rotating heat transfer results obtained in the hot cascade using a traversing pyrometer at a realistic wall-to-coolant temperature ratio. The results are presented for realistic rotational numbers, ranging from 0 to 0.023, and for representative Reynolds number of 20,000 based on the channel diameter. The effect of Coriolis forces is evident with the change of direction of the rotation. A slight negative influence of the crossflow, which increased toward the outer radius of the channel, was recorded in the rig test results. The results presented will assist in better understanding of the screw-shaped swirl cooling technique, providing the next step toward the application of this highly-effective internal cooling method for the leading edges of turbine blades.
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Hoernig, T., and C. Friedrich. "Thread Reinforcement of Screw Connections in Lightweight Design." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-39465.
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Design engineers today desire to develop more lighter and compact components with higher performance capabilities against the background of saving resources. For this purpose, low strength and lightweight metals such Aluminum or Magnesium are preferred on one hand. On the other hand there is an increase in load requirements which needs higher clamp force between these components. In such applications length of thread engagement requires special focus. At the same time from industry perspective it is essential to have effective dimensioning methods to develop new products in shorter time and at a reasonable cost (economics). Besides the increase in length of thread engagement, the tribology of mechanical contacts (i.e. increased friction coefficients and limited loading capacity due to higher contact pressure) plays an important role in the tightening process. The result is that the desired preload is often not achieved with a standardized tightening specification (reasons: high friction decreases preload for same tightening torque by high torsional stresses). In this contribution experimental results of tightening screws with nut components made from aluminum alloys are analyzed for their frictional behavior by using a multi-channel screw assembly test stand. Risks and dangers associated with tightening process are highlighted and suggestions are made for improvement in thread reinforcement. An established method to realize thread reinforcement is using wired thread inserts. For these elements several standards concerning geometry and strength exist but no dimensioning method is available. These thread inserts themselves have a higher strength than the nut thread material and transmit the preload force of the screw with a greater surface area than the original nut component. This leads theoretically to an increase in the load capacity of the nut thread. The approach of existing dimensioning methods by established rules and regulations for the design of bolted connections, e.g. VDI 2230, are not able to predict the behavior of reinforced thread engagements. Hence, an extension for the dimensioning of threaded engagement is essential for modern requirements. Experiments of tightening screw joints with wired thread inserts and with normal thread engagement are comparatively analyzed along with numerical calculations using Finite Element Analysis (FEA). Conclusions are drawn from experimental and FEA results with the perspective of formulating an extended dimensioning method for thread reinforcement of screw connections in lightweight design. These points are interesting for every design engineer, especially in the field of lightweight design.
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Wilczynski, K., and A. Nastaj. "SSEM-AG Computer Model for Optimization of Polymer Extrusion." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-13074.
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The optimization of an extrusion process is a conflicting, multi-objective problem. It is complicated by the number of variables (screw/die geometry, operating conditions, material data) and their non-linear relations, as well as by the opposing criteria, for example extrusion throughput and power consumption. It is difficult to find the global optimum for the process avoiding local optima. There are two approaches to solve the problem, experimental and using a mathematical model of extrusion. Optimization techniques based on an experimentation are time-consuming and very expensive. In this paper we present an optimization methodology based on the Genetic Algorithms (AG), where response surface is given by the extrusion model. A mathematical Single-Screw Extrusion Model SSEM developed at the Warsaw University of Technology is used to predict the extruder behavior, and AG approach is used for optimization. An integrated SSEM-AG system was developed to study optimization of the single-screw extrusion process. Three design criteria (output variables) are selected for optimization: maximum extrusion throughput, minimum power consumption and low melt temperature. As input variables, screw speed, barrel temperature and screw channel depth are chosen.
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Glezer, B., H. K. Moon, and T. O’Connell. "A Novel Technique for the Internal Blade Cooling." In ASME 1996 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-gt-181.
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Development of an adequate air cooling system for the thermally highly loaded leading edge and tip of the blade, that is cost effective and also relatively insensitive to manufacturing tolerances and operating environment continues to be one of the major challenges in advanced gas turbine design. Extensive studies on the convective (including impingement) and film cooling techniques produced remarkable progress in achieving a high cooling effectiveness level for turbine airfoils. However, in the case of turbine blades, application of these techniques has severe limitations. Highly effective impingement cooling needs to be combined with film discharge of the spent air to avoid a negative impact of crossflow on internal heat transfer and also provide additional thermal protection of the surface downstream of the discharge holes. Noticeable aerodynamic penalties, stress concentration and significant increase in manufacturing cost limit application of blade film cooling, particularly for moderately high operating temperatures. Search for a highly effective robust design of internal airfoil cooling which can delay the use of film cooling resulted in the creation of a new technique which is described in this paper. This technique is based on generation of a swirling flow structure in the blade internal leading edge passage. Significant heat transfer augmentation can be achieved when the cooling air is delivered into the leading edge plenum tangentially to the inner concave surface. The best results can be obtained when the swirling flow is allowed to move radially, creating a three-dimensional screw-shaped flow in the plenum. The presented results of the flow and heat transfer studies performed for the practical range of Reynolds numbers for the internal flow show that the leading edge screw-shaped cooling technique provides internal heat transfer rate comparable with impingement coupled with film discharge of the spent air, is more effective than impingement with cross flow and is almost five times higher than heat transfer in the smooth channel.
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Li, Lei, Zhaohua Chang, Xuelian Gu, and Chengli Song. "Design and Research of Interspinous Lumbar Non-Fusion Device." In ASME 2010 5th Frontiers in Biomedical Devices Conference. American Society of Mechanical Engineers, 2010. http://dx.doi.org/10.1115/biomed2010-32064.
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Objective: Long term clinical data showed that lumbar fusion for Lumbar spinal stenosis (LSS) and lumbar disc degeneration (LDD) therapy could change the loads of disc and articular facet and increase the motion of adjacent segments which lead to facet arthropathy and adjacent level degeneration. This study is to design and analyze an interspinous process device (IPD) that could prevent adjacent level degeneration in the LSS and LDD therapy. Method: The IPD was designed based on anatomical parameters measured from 3D CT images directly. The IPD was inserted at the validated finite element model of the mono-segmental L3/L4. The biomechanical performance of a pair of interbody fusion cages and a paired pedicel screws were studied to compare with the IPD. The model was loaded with the upper body weight and muscle forces to simulate five loading cases including standing, compression, flexion, extension, lateral bending and axial rotation. Results: The interbody fusion cage induced serious stress concentration on the surface of vertebral body, has the worst biomechanical performance among the three systems. Pedicle screws and interbody fusion cage could induce stress concentration within vertebral body which leads to vertebral compression fracture or screw loosening. Regarding to disc protection, the IPD had higher percentage to share the load of posterior lumbar structure than the pedicel screws and interbody fusion cage. Conclusion: IPD has the same loads as pedicle screw-rod which suggests it has a good function in the posterior stability. While the IPD had much less influence on vertebral body. Furthermore, IPD could share the load of intervertebral discs and facet joints to maintain the stability of lumbar spine.
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Ishimura, Mitsutoshi, Shunichiro Sawa, Yuya Omiya, and Toshiyuki Sawa. "Mechanism of Screw Thread Loosening in Bolted Joints With Dissimilar Clamped Parts Under Repeated Temperature Changes." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-38077.
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It is well known that bolted joints are sometimes loosened under transverse repeated loadings. Recently, some studies have been carried out on the mechanism of the bolt loosening under transverse repeated loadings. In the present research, the mechanism of bolt loosening was examined for a bolted joint using Junker’s type loosening test machine under transverse repeated loadings. Furthermore, a rotational deformation of bolt axis and nut was analyzed using FEM. As a result, it is found that the rotational load is applied and the bolt loosening occurs due to the deformation between the bolt axis and the nut. The measured change in axial bolt force was fairly good agreement with the numerical results. In addition, the bolt loosening in bolted joints with dissimilar clamped parts was examined under temperature changes. Due to the temperature changes, it is assumed that a relative displacement among the bolt bearing surface and the bearing surfaces of the clamped parts and then it is found that a bolt loosening occurs. In FEM calculations, the behavior of the bolt loosening was examined and found to occur a slight loosening. In the experiments, the bolt loosening was measured under temperature changes. The material of dissimilar clamped parts is assumed steel and aluminum. The thickness of the clamped parts is 10mm. The tendency of the bolt loosening is fairly coincided between the numerical and the measured results. It was observed that the bolt loosening occurred easily as the clamped length (gap length) decreased. In the FEM calculations, the slope θ of the bearing surfaces between the bolt head and the clamped part is assumed to be 0.5 degree to 2 degree. The effects of the slope of the bearing surfaces and on the bolt loosening are examined in the FEM calculations. The calculated results are in a fairly good agreement with the measured results. As the conclusions, 1) the bolt loosening of bolted joints under transverse repeated loadings was elucidated using 3-D FEM calculations, 2) Under repeated temperature changes, it was found that the bolt loosening occurred due to the slips between the bearing surfaces and the interfaces of clamped parts. Using FEM calculations, the behavior of the bolt loosening was elucidated.
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Sawa, Toshiyuki, Mitsutoshi Ishimura, Yasumasa Shoji, and Yusuke Fukuba. "Mechanical Behavior of Rotational Screw Thread Loosening in Bolted Joints Under Repeated Temperature Changes." In ASME 2008 Pressure Vessels and Piping Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/pvp2008-61690.
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Bolted joints have been used in mechanical structures. However, loosening accidents sometimes happen under several types of loadings. Recently, some studies have been conducted on the screw thread loosening in bolted joints. It is verified that bolted joints are loosened when transverse repeated loadings are applied. A lot of parts for preventing the loosening in the joints have been proposed. Among these parts, eccentric nut is especially expected to be the solution for preventing the loosening. Some studies on no rotational loosening in bolted joints under thermal changes have also conducted. However, few studies on rotational screw thread loosening in bolted joints have conducted. In our previous study, mechanism of rotational screw thread loosening in bolted joint under repeated temperature changes was examined. However, the difference in the loosening mechanism between the FEM results and the experimental results was substantial. In this study, the effect of the incline at the bearing surfaces was taken into consideration on the loosening. In addition, the loosening in the bolted joint with the eccentric nut under repeated temperature changes was examined using finite element method (FEM) calculations. Discussion is made on the mechanism and a solution of rotational screw thread loosening in the bolted joints under the repeated temperature changes. The results show that a reduction in axial bolt force was increased when the incline at the bearing surfaces was taken into consideration and the eccentric nut was shown for preventing the bolt loosening.
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Hoernig, T., H. W. Kopfer, and C. Friedrich. "Torque Vibrations in Automatized Screw Assembly: Reasons, Elimination and Virtual Testing." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-62347.
Full textAbstract:
Today the torque controlled tightening method for screw assembly is an established process in industries undertaking large scale productions [12]. In this tightening method an instability of friction during the tightening procedure leads to an imprecise stop of the electronic tightening tool affecting the preload. Besides this heavy noise emission occurs due to vibrations. Because of shorter and shorter cycle times in automated screw assembly, higher precision requirements, new surface pairings (e.g. Cr(VI)-free) with changed coefficients of friction and more complex assemblies with difficult access to the joint, result in an increased number of torque vibrations on automatized screw assembly (also called stick-slip). Due to highly interconnected production flows, the productivity is hereby significantly interrupted. This means significant financial loss because of a small screw which stops the entire production line. This contribution entitles the reasons for the origin of torque vibrations as well as advices for elimination.
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Isele, D., C. Friedrich, and A. Isele. "Analysis of Preload Loss With Corrosion Protection Layers in the Flow of Force." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-66005.
Full textAbstract:
This contribution investigates the tightening behavior and preload loss of bolted joints with painted coating systems for corrosion protection of components. Friction coefficients are measured with test stand, preload loss is measured by strain gauges. Further evaluation is done with optical roughness measurement to see damage of the painted surfaces in contact areas. Resulting from this hints for applications get obvious. Research progress focuses the quantification of preload loss in different applications. Mechanical loads are neglected at that stage because of minor influence as the temperature. To sum up, it can be formulated that the tested, robust coating systems can endure yield-point-tightening of high-strength screws and also exist as a complete and coherent layer after the loosening. Therefore corrosion protection could be guaranteed also after a yield-point-tightening, especially underneath the screw head. This is in particular relevant for applications which require repeated tightening of the same screw. Corrosion protection layers within the flow of force usually change the friction coefficients compared with bare material. This effect influences the assembly of bolted connections dominantly. Controlling the assembly process is getting more difficult because of the increasing scattering from steering parameters, like torque or angle. There might be huge deviations, up to a factor of 6.2, between torque values of a similar assembly process. Therefore process safety cannot be guaranteed, especially if their values miss originally defined tolerances. To overcome these difficulties it is necessary to use the right assembly method as well as the right coating system. After our opinion the yield-point controlled tightening is the only method which leads to a safe assembly preload, even with coated parts. If the preload loss will be acceptable depends on the coating system and the external conditions.